1. Field of the Invention
The present invention relates to a communication system and more particularly to a communication system using P2P (Point to Point) connections.
2. Description of the Prior Art
With advancement of network technology, many electronic products can access the Internet to have online services, such as remote control and online update. For example, a U.S. Pat. No. 6,373,851 disclosed a technology using the Ethernet to control electronic devices, wherein a communication system comprises a first communicating medium, an Ethernet polling server, and a plurality of Ethernet client stations. The Ethernet polling server has a transmitter connecting with the first communicating medium. The transmitter and the first communicating medium can bidirectionally communicate with each other. The Ethernet client stations interconnect with each other, and each of them has a transmitter containing a second communicating medium. The second communicating medium would not send any signal to the first communicating medium unless required by the Ethernet polling server. However, the second communicating medium can receive signals from the first communicating medium anytime. The prior art is based on a traffic controlling device and constrained by the minimum transmission rate and the maximum recommended distance of the Ethernet. Therefore, the prior art has a greater transmission range and can prevent from the transmission delay and collision of the terminal devices.
The Internet connection between proximal devices and terminal devices has been a very popular technology. If home electric appliances are intended to link with the network, they need wiring with network cables and thus consume more manpower. Therefore, there were developed technologies using the power network as the communication network. For example, a US publication No. 2005/0047379 disclosed a technology using wireless wideband or power cables to transmit audio/video contents. The device of the prior art has a content server receiving AV information and converting the information into PLC (Power Line Communication)—compatible signals. The device also has a PLC/UWB (Ultra-Wide Band) module able to establish a link with a signal transceiver of an electric appliance. Thereby, the electric appliance can receive information from the network and can be controlled by a remote device via the power lines without using any network cables.
A US publication No. 2004/0186908 also disclosed a PLC technology, wherein a power plug comprises AC power cords, network cables and a PLC adaptor. In another embodiment of the prior art, the power plug further has an AC/DC converter besides the AC power cords, network cables and PLC adaptor.
A China patent No. CN100389602 entitled “a camera system and a controlling method of the same” using a PLC technology for surveillance systems. In the prior art, a camera module connects with a PLC adaption module. The PLC adaption module receives the AV information recorded by the camera module, modulates the AV information and transmits the modulated AV information via the power lines. At the same time, the modulated signals received from the power lines are demodulated to obtain the control signals for controlling the camera module. The PLC adaption module includes a camera signal processing unit, a digital multimedia information compressing unit, an Ethernet adaption unit and a first PLC modulation/demodulation unit. The camera signal processing unit and the digital multimedia information compressing unit compress or convert the format of the image signals output by the camera module. The Ethernet adaption unit converts the signals into Ethernet signals. The first PLC modulation/demodulation unit loads the Ethernet signals on carrier waves able to be transmitted via the power lines. Thereby, the AV signals of the camera module can be transmitted to the monitoring side via the power lines.
The PLC technology exempts electric appliances from being wired with network cables and enables them to directly link with the network via power lines. In the conventional technology, the router assigns an IP (fixed IP or floating IP) to the electric appliance, and the electric appliance needs a server to allow the electric appliance side and the surveillance/control side (the user side) to exchange data. In the conventional technology, the surveillance/control side cannot link to the appliance unless it remembers the IP or domain name of the appliance or server. Further, the user has to renew the IPs or domain names by himself when the appliances or servers increase or when the IPs thereof are changed. The user should be very troubled by the complicated process. Furthermore, as the domain names or IPs of the electric appliances or servers are open to the public, they are likely to be sniffed or damaged by hackers. Therefore, the conventional remote surveillance/control technology still has some problems have to be overcome.